Methods and apparatus for contacting liquid with granular contact material



METHODS AND APPARATUS FOR CONTACTING LIQUID WITH GRANULAR CONTACTMATERIAL Filed Aug. 11, 1950 July 6, 1954 I D o ms 2,683,109

' INVENTOR '4 David Z. My?

Patented July 6, 1954 METHODS AND APPARATUS FOR CONTACT- ING LIQUID WITHGRANULAR CONTACT MATERIAL David E; Norris, Philadelphia, Pa., assignorto Houdry Process Corporation, Wilmington, Del., a corporation ofDelaware Application August 11, 1950, Serial No. 178,766

9 Claims.

1 The present invention relates to systems and methods for theconversion of liquid hydrocarbons by contacting such hydrocarbons withgranular contact material. Typical of the conversion processes andsystems to which the invention is applicable is the cracking ofrelatively high boiling liquid hydrocarbons to gasoline using granularabsorptive hydrocarbon cracking catalyst or the viscosity breaking orcoking of such hydrocarbons using relatively catalytically inertgranular solids of the type known as heat carriers.

The use of higher boiling fractions of the crude oil, such as tarseparator bottoms, reduced crudes, heavy fuel oil and the like, ascharging stock for the preparation of gasoline and/or light fuel oilpresents difliculties due to the ease with which such fractionsthermally decompose to form coke whether or not volatile crackedproducts are also formed. For example, many of such fractions coke upthe tubes of heating furnaces when heated to temperatures of 850 F. orabove and hence, even if vaporizable at temperatures of 900 to 1000 F.,cannot be handled as vapor because such a practice would result in toofrequent shutdowns oi the heating equipment. As a consequence, it hasbeen the practice to contact such charging stocks in liquid form withhot granular contact material under conditions such that the liquidhydrocarbons are decomposed to volatile products with an attendantformation of a hydrocarbonaceous deposit (which includes very heavy,non-vaporizable hydrocarbons) on the contact material. Thehydrocarbonaceous deposit on the contact material further decomposesduring the conversion period to form volatile hydrocarbons and coke, thelatter being removed by combustion with an oxygen containing gas duringa subsequent regenerative operation.

The prior art has diligently and actively sought methods for efiicientlycontacting liquid hydrocarbons with moving granular contact materialunder conditions that insure even distribution of the liquid on thetotal mass of contact material. A commercially successful methodinvolves projecting liquid hydrocarbons toward a sheetlike curtain offalling particles of granular contactmaterial, which curtain has such adensity and thickness as to intercept the liquid hydrocarbons directedthereto, as disclosed and claimed in copending application Serial No.766,714, filed August 6 1947, in the name of Reuben T, Savage, nowPatent No. 2,548,912. This method is successful in effecting contactbetween liquid hydrocarbons and moving contact material, an atomizingnozzle of one of several special designs being used to projecthydrocarbons. However, it was discovered that the conditions of contactchanged when the stream of hydrocarbons passing through the nozzlecontained varying amounts of vapor, such as are Within the necessaryrange of commercial operation, and led to undesirable effects, dueprincipally to variable flow through the nozzle. At excessive nozzlevelocities, the contact material in the curtain is subject to outwarddisplacement with resultant particle-to-particle and particleto-wallcollision resulting in attrition. At very low nozzle velocities, theliquid fails, at least in part, to reach the curtain and hence is notdisindependent of the physical properties and amount of the liquidhydrocarbons, thus providing an improved and. more flexible method ofoperation.

In accordance with the present invention, I flow a stream of fluidcomprising gas'and liquid hydrocarbons to and in a laterally confinedzone within the conversion or cracking zone in such a manner that thestream of fluid rotates in said confined zone and concentrates orseparates the liquid hydrocarbons atthe periphery of the confined zone.The separated liquid flows downwardly into contact with particles ofcontact material. As described below, I can flow separated liquidhydrocarbons convergently toward the center of a confined zone so as tocontact the outer periphery of an annular stream or layer of contactmaterial flowing within said confined zone.

.The principles involved in the present invention are set forth indetail below in connection with the description of the drawing in whichthe application of a preferred embodiment of the present invention to acatalytic cracking system is shown. It is to be understood that thispreferred embodiment and the application of the invention to a catalyticcracking system are to be regarded as illustrating the present inventionrather than restricting its scope.

In the drawing:

Figure 1 is a vertical View of a vessel containing a moving bed of solidparticles with portions of the vessel broken away for a better view ofthe relationship of the parts;

Figure 2 is a transverse section of the vessel illustratedin Figure 1taken along the lines 2-2 showing the relationship of the parts of theapparatus at this level. I

Figure 3 is a transverse section of a gas-liquid separating device shownin Figures 1 and 2 as taken along the lines 3-3 in Figure 1.

Shown in Figure l is a closed vertical elongated reaction housing orvessel indicated generally at 26 which housing comprises a contact orcracking chamber or zone containing a downwardly moving bed of solidparticles or hydrocarbon cracking catalyst, as indicated generally at 2l. Fluent solid particles in the size range of from about 0.05 to about0.5 inch and comprising freshly regenerated solid hydrocarbon crackingcatalyst, such as acid activated montmorillonite clay, syntheticsilica-alumina gel in pellet or bead form or other solid refractorycompositions known by those skilled in the art to be hydrocarboncracking catalysts, are introduced to housing by conduit 22 at the topthereof and form a bed 23 in a catalyst introduction, storage or sealingchamber 24 in the top of the housing above horizontal bafile or tubesheet 25 as shown. Part of the particles in bed 23 flow from storagechamber 21,, to the cracking or contacting chamber through conduits 26,which are arranged equidistantly from the center of tube sheet 25, ontothe surface of bed 21. Another portion, preferably the major portion,such as from 50 to 90 percent, and in some cases all of the particles,flow through conduit 21.

Particles discharge from the end of conduit 27, to form a bed 28, theend of conduit 21 terminating within the cracking zone or chamber (whichmay be considered as having its upper limit at tube sheet 25) and abovethe surface of bed iii. The sides of bed 28 are confined by acylindrical baffle or wall 29 which is supported and positioned bybraces 3i within a surrounding gas-liquid separation member or deviceindicated generally at 32. Afilxed to the bottom of cylindrical wall 29,as by welding, is a circular ring 33. Positioned concentrically in thecenter of the inner periphery of ring 33 is a conical baffle 34?-positioned with its apex upward. Conical baffie 34, which is supportedby braces 35, has a circular outer periphery which is smaller than theinner periphery of ring 33, these two members cooperating to define anannular particle metering zone, passageway or discharge orifice 36.

Annular passageway 36 has a lesser discharge capacity than that ofconduit 2'1 so that the particles of catalyst move from bed 23 topassageway 36 in choked or compact flow. The width and area of annularpassageway 36 are selected so that an amount of catalyst dischargestherefrom sufficient to adsorb the liquid hydrocarbons later contactedand/ or provide adequate heat capacity for the desired vaporization ofsuch hydrocarbons. The particles of catalyst discharge from passageway35 and fall downwardly and unobstructedly to the frusto-conical bottomwall Sl of device 32. Because wall 3? converges and is open at thebottom, the particles travel in a converging path until they reach thebottom of wall 3! where they fall freely and unobstructedly downwardlyto the surface of bed 2i. The upper surface of wall 31 may be smooth sothat the wall acts as a deflecting baflie down which the particles slideor roll freely. Alternatively, obstructions to particle flow, such as agrating, may be placed on the upper surface of wall 3'! so as to createa thick, relatively slow moving layer of particles, which flows down thebottom wall.

Hydrocarbon vapors produced by contact with the catalyst in a mannerdescribed below, to-

gether with any hydrocarbon vapors introduced to the top of theconversion zone through conduit 38, pass downwardly through bed 29 andare disengaged from the bed of particles at the bottom of the crackingzone or chamber by methods known to the art. The disengaged vapors arewithdrawn through conduit 39 for appropriate processing for theproduction of gasoline and/or light fuel oil and other products. Thehydrocarbon vapors are confined within the cracking zone or chamber byintroducing a sealing gas such as steam, inert flue gas and the like, tostorage or sealing chamber 24 through conduit 40 at a pressure slightlyabove the pressure in the cracking zone. A portion of the sealing gaspasses upwardly through the compact column of catalyst in conduit 22while the remainder passes downwardly through the compact columns ofcatalyst in conduits 26 and 21.

The particles of catalyst thereafter pass downwardly through a purgingzone in which they are contacted with steam, spent flue gas or otherinert non-oxidizing gases introduced through conduit 4| through gasdistribution devices known to the art (not shown in the drawings). Thepurging gas also serves to confine the hydrocarbon vapors to theconversion zone in a similar manner to that described above inconnection with chamber 24. The purged catalyst, which contains adeposit of coke, is removed from housing 20 through conduit 32 and sentto a regeneration zone in which the coke deposit is removed by contactunder combustion conditions with an oxidizing gas, the regeneratedcatalyst being returned to housing 2d for further use therein.

In accordance with the embodiment of the invention shown in the drawing,a stream of fluid comprising gas, the nature of which is describedbelow, and liquid hydrocarbons is passed from the exterior of vessel 20to the cracking chamber through a conduit 43 which communicates with theinterior of gas-liquid separation device Conduit 43 can enter thecracking chamber in any convenient manner; for example, as shown inFigure l, where it enters the cracking chamber horizontally through thesidethereof. As shown in Figures 2 and 3, conduit 43 is posi ioned sothat the stream of fluid passing therethrough enters the interior ofgas-liquid separation device 32 tangentially to the upper verticalcylindrical wall 44 of device 32, which wall terminates at its upper endin a small outwardly flaring section 45, Support braces 46 are attachedto the top flaring section so as to support and position the deviceconcentrically with respect to the annular particle metering passageway38, the latter being spaced from wall 44.

Because of the tangential method of introduction, the stream of gas andliquid hydrocarbons introduced to gas-liquid separation device 32rotates therein so that the liquid hydrocarbons are thrown against thewall or periphery thereof by centrifugal force. The separated liquidhydrocarbons fiow down the sides of wall M, which serves to laterallyconfine the zone in which the gas and liquid hydrocarbons are separated,and thence to the frusto-conical bottom 3? where they flow inwardly aswell as downwardly. As the liquid hydrocarbons flow down bottom 3'? incentrally converging flow, they contact the par ticles of catalystfalling downwardly from annular passageway 36 and are at least partiallyvaporized by the particles which are at a temperature, such as about 50to 500 F., higher than that of the liquid hydrocarbons. The portion ofthe liquid hydrocarbons that are vaporized fiows upwardly out of the topof gas-liquid separation device 32 and then downwardly to and throughbed 21 as previously described. Any unvaporized liquid hydrocarbons areabsorbed by the absorptive particles of catalyst.

As stated above, gas and liquid hydrocarbons to be cracked areintroduced to conduit 43. Such liquid hydrocarbons are not vaporizableat the temperature existing in the stream of fluid in conduit 43, as,for example, hydrocarbon fractions having initial boiling point and/ordew point above about 850 F. The gas can be gaseous or vaporoushydrocarbons or any gas that is readily available, cheap and unreactivewith hydrocarbons, such as steam, spent flue gas,nitrogen and the like,although steam is preferred, or a mixture of hydrocarbon vapors or gasand unreactive gas may be employed. Suitable hydrocarbon vapors mayinclude those from the same source as that of the liquid hydrocarbons;thus, for example, a wide cut portion of crude oil may be heated toproduce liquid and vapors Alternatively, the hydrocarbon vapors or gasescan be from a separate source or process, such as from the same or othercracking processes, and can include light hydrocarbons, such as propaneor butane. The gas and liquid hydrocarbons may be at the same ordifferent temperatures when blended, if from different sources, or theymay be blended and thereafter heated together.

As can be seen in Figure 1, the particles fall only a short distance,such as 6 to 18 inches, from annular particle metering zone 36 onto thesurface of the inwardly converging bottom 3! of device 32 and thereafterflow a short distance, such as from about 0.5 to 3 feet, onto thesurface of bed 2|. Under these conditions, the distance from which theparticles fall is such that the velocity of the falling particles, dueto acceleration by gravity, is low when they impinge on either metallicsurface 31 or on therelatively static particles on the surface of bed2|. Indeed the total distance over which gravity exerts its full force(from annular passageway 36 to the surface of bed 2i) is relativelyshort and hence the maximum velocity of the particles is low. Theresulting impact is small, with a consequent low rate of attrition ofthe particles, which are frangible when the impact is too great. As aresult, the present invention achieves efi'lcient contact with theliquid hydrocarbons and catalyst particles under conditions such thatthe rate of attrition of the particles is desirably low.

The volume of gas utilized to carry the liquid hydrocarbons as a streamis preferably relatively large compared to the volume of the liquidhydrocarbons so as to produce a considerable velocity of the stream offluid in conduit :44 and hence a considerable velocity of rotation indevice 32. In vessels of commercial size where the diameter of wall A lis from 2 to 4 feet and the diameter of bed 2! is from 4 to 20 feet,efiicient separation of the liquid hydrocarbons is achieved when thelinear velocity of the stream of fluid entering device 32 is preferablymore than feet per second, such as from about 20 to 100 feet per second.Such velocities may be employed over a wide range of ratios of vaporvolume'to liquid volume, such as from about 10 to 1000. Theeffectiveness of the present invention over a wide range of vapor volumeto liquid volume is extremely advantageous in that, without any physicalchanges in the apparatus, the amount of liquid 6.. hydrocarbons chargedcan be quickly varied, without loss in efficiency of contact orundesirable side effects such as high catalyst attrition rates.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

- I claim asmy invention:

1. In a hydrocarbon conversion process wherein granular contact materialis contacted with hydrocarbons, at least partially in a liquid phase,while gravitating through a conversion zone, the method for contactingthe liquid hydrocarbons with said contact material which comprises thesteps of: introducing a confined stream comprising gas and liquidhydrocarbons into a laterally confined separating zone centrallypositioned in the upper region of said conversion zone, dischargingseparated gas from the upper end of said separating zone into saidconversion zone, passing separated liquid hydrocarbons downwardly andinwardly as a circumferentiallycomplete hollow liquid stream toward acentral discharge outlet at the lower end of said separating zone, saidhollow liquid stream flowing as an inwardly-moving supported layer in atleast the lower portion of its path through said separating zone,introducing said contact material centrally into said separating zone asan annular curtain of freely-falling particles at a level below thelevel of hydrocarbon introduction, passing said curtain of contactmaterial concentrically downward within said 'hollow liquid stream anddepositing the same onto said inwardly-moving supported layer of liquidhydrocarbons, and discharging said contact material containing liquidhydrocarbons as a freelyfalling stream from said central dischargeoutlet into said conversion zone.

2. A method as defined in claim 1 wherein said gas and liquidhydrocarbons introduced into said separating zone are caused to rotateabout a vertical axis at a velocity sufficient to form saidcircumferentially-complete hollow liquid stream and to separate said gastherefrom by centrifugal action.

3. A method as defined in claim 2 wherein said centrifugal action iseffected by introducing said stream of gas and liquid hydrocarbonstangentially into said separating zone as a highvelocity stream.

4. A method as defined in claim 1, in which said freely-falling streamof contact material discharged from said discharge outlet of theseparating zone is deposited on the surface of a compact moving bed ofsaid contact material.

5. A method as defined in claim 4, in which said contact material is ata temperature sumcient to vaporize at least a portion of said liquidhydrocarbons upon deposit of said freely-falling contact material ontosaid inwardly moving layer of liquid hydrocarbons, and wherein all thegaseous material is passed downwardly through said in open communicationat its upper end with said chamber, said cylindrical member extendingabove and below said contact material inlet means and having a lowerconverging wall portion terminating in a central opening axially alignedwith and spaced a distance below said contact material inlet means, saidopening being of substantially smaller diameter than the annular locusof discharge from said contact material inlet, and fluid inlet meansextending through the wall of said chamber and into said cylindricalmember and arranged to discharge horizontally and tangentially withinthe latter at a level above said contact material inlet, and gas outletmeans in the lower region of said chamber.

7. Apparatus as defined in claim 6, in which said contact material inletmeans is a vertical conduit extending downwardly into said contactingzone from a contact material supply chamber located above saidcontacting chamber, 20

and including means at said contact material inlet for metering 'theflow of contact material in said annular stream.

8. The steps of claim 1 characterized in that said gas'comprises steam.

9. The steps of claim 1 characterized in that said gas compriseshydrocarbon vapors.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,316,770 Corthesy Sept. 23, 1919 2,286,503 Ocon June 16, 19422,493,035 Savage Jan. 3, 1950 2,515,155 Munday July 11, 1950 2,548,912Savage Apr. 1'7, 1951 2,556,514 Bergstrom June 12, 1951 2,574,850Utterback et a1 Nov. 13, 1951 2,593,495 Shimp Apr. 22, 1952

1. IN A HYDROCARBON CONVERSION PROCESS WHEREIN GRANULAR CONTACT MATERIALIS CONTACTED WITH HYDROCARBONS, AT LEAST PARTIALLY IN A LIQUID PHASE,WHILE GRAVITATING THROUGH A CONVERSION ZONE, THE METHOD FOR CONTACTINGTHE LIQUID HYDROCARBONS WITH SAID CONTACT MATERIAL WHICH COMPRISES THESTEPS OF: INTRODUCING A CONFINED STREAM COMRISING GAS AND LIQUIDHYDROCARBONS INTO A LATERIALLY CONFINED SEPARATING ZONE CENTRALLYPOSITIONED IN THE UPPER REGION OF SAID CONVERSION ZONE, DISCHARGINGSEPARATED GAS FROM THE UPPER END OF SAID SEPARATING ZONE INTO SAIDCONVERSION ZONE, PASSING SEPARATED LIQUID HYDROCARBONS DOWNWARDLY ANDINWARDLY AS A CIRCUMFERENTIALLYCOMPLETE HOLLOW LIQUID STREAM TOWARD ACENTRAL DISCHARGE OUTLET AT THE LOWER END OF SAID SEPARATING ZONE, SAIDHOLLOW LIQUID STREAM FLOWING AS AN INWARDLY-MOVING SUPPORTED LAYER IN ATLEAST THE LOWER PORTION OF ITS PATH THROUGH SAID SEPARATING ZONE,INTRODUCING SAID CONTACT MATERIAL CENTRALLY INTO SAID SEPARATING ZONE ASAN ANNULAR CURTAIN OF FREELY-FALLING PARTICLES AT A LEVEL BELOW THELEVEL OF HYDROCARBON INTRODUCTION, PASSING SAID CURTAIN OF CONTACTMATERIAL CONCENTRICALLY DOWNWARD WITHIN SAID HOLLOW LIQUID STREAM ANDDEPOSITING THE SAME ONTO SAID INWARDLY-MOVING SUPPORTED LAYER OF LIQUIDHYDROCARBONS, AND DISCHARGING SAID CONTACT MATERIAL CONTAINING LIQUIDHYDROCARBONS AS A FREELYFALLING STREAM FROM SAID CONTACT DISCHARGEOUTLET INTO SAID CONVERSION ZONE.